Catalyst modification to control polymer architecture

ABSTRACT

By controlling the ratio of catalyst components or the type of activator the homogeneity of a polymer produced using a single site catalyst may be improved.

The present disclosure relates to a method to improve the homogeneity ofa copolymer produced in a solution polymerization using a single sitecatalyst in the presence of aluminoxane and an ionic activator. Inconducting a solution phase polymerization, there is a tradeoff betweencatalyst activity and circulation rate through the reactor. It isdesirable to have a highly reactive catalyst or catalyst system. In someinstances, the polymer produced may have a degree of inhomogeneity inthat the polymer has up to 10 wt. % or more of a component having amolecular weight of greater than 10^(5.3). In further embodiments, thiscomponent may have a molecular weight greater than 10^(5.5). It may bedesirable to reduce the amount of this component.

There are a number of copolymers produced in the presence of a singlesite catalyst which are “bimodal”. Typically, these resins have a TREFhaving an inflection point at an elution temperature of about 90° C. to93° C., typically 90° C. to 91° C. The fraction may have a weightaverage molecular weight ranging from about 10^(5.3) to 10^(5.5).Without wishing to be bound by theory, it is believed such copolymerscomprise two homogeneous copolymer components having a differentmolecular weight and/or density. Provided that the fraction of acopolymer produced using a single site catalyst having an elutiontemperature above about 90° C. is less than about 10 wt. %, the totalcopolymer is relatively homogeneous. As the amount of this component inthe copolymer increases, there may associated issues of processing andproduct homogeneity. This is particularly evident in polymers having adensity up to about 0.940 g/cc. However, the processes described hereinare equally applicable to higher density polymers having a density up toabout 0.960 g/cc.

U.S. Pat. No. 6,984,695 teaches the solution phase polymerization ofpolyethylene in a solution phase in the presence of a phosphiniminecatalyst and an activator. The patent teaches, at Col. 13, lines 60-65,that the monomer feeds and the position of the monomer feed portsrelative to the catalyst feed port was varied to examine the effect ofthese variables upon the microstructure of the polymer. Although theratio of Al/Ti varied from 205:1 to 65:1, the weight % of the“heterogenized” fraction did not appear to change significantly.

U.S. Pat. No. 6,777,509, issued Aug. 17, 2004 to Brown et al., assignedto NOVA Chemicals (International) S.A., teaches using a trialkylaluminum compound in a catalyst system comprising a phosphiniminecomplex to produce olefin copolymers with broadened molecular weightdistributions, Mw/Mn, of greater than 2.0. In some embodiments of theinvention disclosed herein, copolymers with narrow Mw/Mn (ranging from1.7 to 2.2) are produced using a catalyst system comprising aphosphinimine complex, a boron activator and an aluminoxane. None of theabove art discusses a method for improving the homogeneity of thecopolymer produced when using single site catalyst systems by varyingthe ratios of the catalyst components or by changing the boronactivator.

In some embodiments, the present disclosure seeks to provide a simplemethod for improving the homogeneity of a copolymer prepared in thepresence of a single site catalyst system.

In one embodiment, a method is provided to increase the homogeneity of acopolymer by reducing the amount of the component eluting at atemperature of greater than 90° C., in the temperature rising elutionfractionation analysis wherein the copolymer is produced using asolution polymerization process in the presence of a catalyst systemcomprising:

1. transition metal catalyst of the formula:

(L)_(n)-M-(X)_(p)

wherein M is a transition, for example a transition metal selected fromTi, Hf and Zr; L is a monoanionic ligand selected from acyclopentadienyl ligand, a indenyl ligand and a fluorenyl ligand whichligands are unsubstituted or up to fully substituted with one or moresubstituents selected from chlorine atoms, fluorine atoms and C₁₋₄ alkylradicals which are unsubstituted or which may be substituted withchlorine or fluorine atoms, and a phosphinimine ligand; X is amonoanionic ligand from the group C₁₋₄ alkyl radicals and chlorine atom;n may be from 1 to 3, and p may be from 1 to 3, provided that the sum ofn+p equals the valence state of M, and further provided that two Lligands may be bridged by a silyl radical or a C₁₋₄ alkyl radical;

2. a boron activator capable of ionizing the transition metal complexselected from:

-   -   (i) compounds of the formula [R⁵]⁺ [B(R⁷)₄]⁻ wherein B is a        boron atom, R⁵ is a cyclic C₅₋₇ aromatic cation or a triphenyl        methyl cation and each R⁷ is independently selected from phenyl        radicals which are unsubstituted or substituted with from 3 to 5        substituents selected from a fluorine atom, a C₁₋₄ alkyl or        alkoxy radical which is unsubstituted or substituted by a        fluorine atom; and a silyl radical of the formula —Si—(R⁹)₃;        wherein each R⁹ is independently selected from a hydrogen atom        and a C₁₋₄ alkyl radical; and    -   (ii) compounds of the formula [(R⁸)_(t) ZH]⁺[B(R⁷)₄]⁻ wherein B        is a boron atom, H is a hydrogen atom, Z is a nitrogen atom or        phosphorus atom, t is 2 or 3 and R⁸ is selected from C₁₋₈ alkyl        radicals, a phenyl radical which is unsubstituted or substituted        by up to three C₁₋₄ alkyl radicals, or one R⁸ taken together        with the nitrogen atom may form an anilinium radical and R⁷ is        as defined above; and    -   (iii) compounds of the formula B(R⁷)₃ wherein R⁷ is as defined        above;

3. an aluminoxane of the formula (R⁴)₂AlO(R⁴AlO)_(m)Al(R⁴)₂ wherein eachR⁴ is independently selected from C₁₋₄ alkyl radicals, m is from 3 to 50and comprising keeping the temperature and mixing conditions in thereactor constant and adjusting one or more of:

-   -   a) the ratio of components 2 and 3; and    -   b) changing component 2.

In a further embodiment, in the catalyst, n is 2.

In a further embodiment, one L is a phosphinimine ligand of the formula:

wherein each R³ is independently selected from a hydrogen atom; ahalogen atom; C₁₋₁₀ hydrocarbyl radicals which is unsubstituted by orfurther substituted by a halogen atom; a C₁₋₈ alkoxy radical; a C₆₋₁₀aryl or aryloxy radical; and an amido radical which is unsubstituted orsubstituted by up to two C₁₋₁₀ hydrocarbyl radicals.

In a further embodiment, the reaction temperature is from 110° C. to180° C. and the pressure is from 6,000 kPa to 22,000 kPa.

In a further embodiment, the starting ratio of catalyst componentsaluminoxane:catalyst:ionic activator is 100:1:greater than 1.1 and isreduced to 50-100:1:0.3-1.05.

In a further embodiment, the ionic activator is selected fromtriphenylcarbenium tetrakis(pentafluorophenyl)borate (sometimes referredto as trityl borate) and tris(pentafluorophenyl)borane.

In a further embodiment, the aluminoxane is methyl aluminoxane.

In a further embodiment, the catalyst is cyclopentadienyltri-tert-butyl-phosphinimine titanium dichloride.

In a further embodiment, the catalyst is alkylated within ten minutesprior to use.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is TREF profiles for Products 1A, 2A, and 3A.

FIG. 2 is TREF profiles for Products 1B, 2B, and 3B.

FIG. 3 is TREF profiles for Products 4A, 5A, and 6A.

FIG. 4 is TREF profiles for Products 4B, 5B, and 6B.

FIG. 5 is GPC profiles for Products 1B, 2B, and 3B.

FIG. 6 is GPC profiles for Products 4B 5B, and 6B.

FIG. 7 is GPC profiles of high density fractions from PREP-TREFseparation.

NUMBERS RANGES

Other than in the operating examples or where otherwise indicated, allnumbers or expressions referring to quantities of ingredients, reactionconditions, etc. used in the specification and claims are to beunderstood as modified in all instances by the term “about”.Accordingly, unless indicated to the contrary, the numerical parametersset forth in the following specification and attached claims areapproximations that can vary depending upon the properties that thepresent invention desires to obtain. At the very least, and not as anattempt to limit the application of the doctrine of equivalents to thescope of the claims, each numerical parameter should at least beconstrued in light of the number of reported significant digits and byapplying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical values, however, inherently contain certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements.

Also, it should be understood that any numerical range recited herein isintended to include all sub-ranges subsumed therein. For example, arange of “1 to 10” is intended to include all sub-ranges between andincluding the recited minimum value of 1 and the recited maximum valueof 10; that is, having a minimum value equal to or greater than 1 and amaximum value of equal to or less than 10. Because the disclosednumerical ranges are continuous, they include every value between theminimum and maximum values. Unless expressly indicated otherwise, thevarious numerical ranges specified in this application areapproximations.

All compositional ranges expressed herein are limited in total to and donot exceed 100 percent (volume percent or weight percent) in practice.Where multiple components can be present in a composition, the sum ofthe maximum amounts of each component can exceed 100 percent, with theunderstanding that, and as those skilled in the art readily understand,the amounts of the components actually used will conform to the maximumof 100 percent.

Solution Phase Polymerization

Solution processes for the (co)polymerization of ethylene are well knownin the art. These processes are conducted in the presence of an inerthydrocarbon solvent, for example, a C₅₋₁₂ hydrocarbon which may beunsubstituted or substituted by a C₁₋₄ alkyl group, such as pentane,methyl pentane, hexane, heptane, octane, cyclohexane, methycyclohexaneand hydrogenated naphtha. An example of a suitable solvent which iscommercially available is “Isopar E” (C₈₋₁₂ aliphatic solvent, ExxonChemical Co.).

The polymerization is conducted at temperatures from about 80° C. up toabout 220° C., in some embodiments, from about 120° C. to 220° C., inalternate embodiments from 120° C. to 180° C. and, in furtherembodiments, from 160° C. to 210° C. Pressures for solutionpolymerization are, for example, less than about 6,000 psi (about 42,000kilopascals or kPa), and, in some embodiments, may range from about 870psi to 3,000 psi (about 6,000 to 22,000 kPa).

In some embodiments, two reactors are used. The polymerizationtemperature in the first reactor is from about 80° C. to about 180° C.(for example, from about 120° C. to 160° C.) and the second reactor isoperated at a higher temperature (up to about 220° C.).

Suitable monomers for copolymerization with ethylene include C₄₋₁₀ alphaolefins. In some embodiments, the comonomers include alpha olefins whichare unsubstituted or substituted by up to two C₁₋₆ alkyl radicals.Illustrative non-limiting examples of such alpha-olefins are one or moreof propylene, 1-butene, 1-pentene, 1-hexene, 1-octene and 1-decene. Insome embodiments, the comonomer is 1-octene.

Catalyst System

The catalyst systems disclosed herein comprise a catalyst, a co-catalystand an activator or an ionic activator.

The Catalyst

The catalyst is a transition metal catalyst of the formula:

(L)_(n)-M-(X)_(p)

wherein M is a transition metal, for example a transition metal selectedfrom Ti, Hf and Zr; L is a monoanionic ligand selected from acyclopentadienyl type ligand, as defined below, a hetero atom ligand ofthe formula J (R)_(x-2) wherein J is selected from a nitrogen atom, aphosphorus atom, a carbon atom and a silicon atom and each R isindependently a C_(1-20,) or, for example, C₁₋₆ hydrocarbyl radicalwhich is unsubstituted or substituted by one or more halogen, or, forexample, chlorine or fluorine atoms and x is the coordination number ofJ, and a phosphinimine ligand; X is a monoanionic ligand from the groupC₁₋₄alkyl radicals and chlorine atom; n may be from 1 to 3, and p may befrom 1 to 3, provided that the sum of n+p equals the valence state of M,and further provided that two L ligands may be bridged by a silylradical or a C₁₋₄ alkyl radical;

The term “cyclopentadienyl type ligand” refers to a 5-member carbon ringhaving delocalized bonding within the ring and typically being bound tothe active catalyst site, for example, a group 4 metal (M) throughη⁵-bonds. The cyclopentadienyl ligand may be unsubstituted or up tofully substituted with one or more substituents selected from C₁₋₁₀hydrocarbyl radicals which are unsubstituted or further substituted byone or more substituents selected from a halogen atom and a C₁₋₄ alkylradical; a halogen atom; a C₁₋₈ alkoxy radical; a C₆₋₁₀ aryl or aryloxyradical; an amido radical which is unsubstituted or substituted by up totwo C₁₋₈ alkyl radicals; a phosphido radical which is unsubstituted orsubstituted by up to two C₁₋₈ alkyl radicals; silyl radicals of theformula —Si—(R)₃ wherein each R is independently selected from hydrogen,a C₁₋₈ alkyl or alkoxy radical, C₆₋₁₀ aryl or aryloxy radicals; andgermanyl radicals of the formula Ge—(R)₃ wherein R is as defined above.

In one embodiment, the cyclopentadienyl-type ligand is selected from acyclopentadienyl radical, an indenyl radical and a fluorenyl radicalwhich radicals are unsubstituted or up to fully substituted by one ormore substituents selected from a fluorine atom, a chlorine atom; C₁₋₄alkyl radicals; and a phenyl or benzyl radical which is unsubstituted orsubstituted by one or more fluorine atoms.

Phosphinimine ligands have formula:

wherein each R³ is independently selected from a hydrogen atom; ahalogen atom; hydrocarbyl radicals, for example, C_(1-10,) which areunsubstituted by or further substituted by one or more halogen atoms;C₁₋₈ alkoxy radicals; C₆₋₁₀ aryl or aryloxy radicals; amido radicals;silyl radicals of the formula:

—Si—(R³)₃

wherein each R³ is as defined above; and a germanyl radical of theformula:

—Ge—(R³)₃

wherein R³ is as defined above;

In some embodiments, the phosphinimine ligands are those in which eachR³ is a hydrocarbyl radical, for example, a C₁₋₆ hydrocarbyl radical, insome embodiments a C₁₋₄ hydrocarbyl radical in further embodiments R³ isa t-butyl ligand.

In some embodiments, n is 2 and each L is a cyclopentadienyl ligand. Insuch embodiments, the catalyst would be a conventional metalloceneligand. If bridged the catalyst would be a bridged metallocene. In otherembodiments, one L is a cyclopentadienyl ligand and one L is a ligand ofthe formula J (R)_(x-2) and if the ligands are bridged, the catalystwould be a constrained geometry catalyst. In other embodiments, n is 2and one L is a cyclopentadienyl ligand and the other L is aphosphinimine ligand.

In some embodiments, the catalyst has the formula

wherein M is selected from Ti, Zr and Hf; Pl is a phosphinimine ligandas described above; L is a monoanionic cyclopentadienyl-type ligand asdescribed above, X is independently selected from activatable ligands; mis 1 or 2; n is 0 or 1; p is an integer and the sum of m+n+p equals thevalence state of M.

Activatable ligands X may be selected from a halogen atom, C₁₋₄ alkylradicals, C₆₋₂₀ aryl radicals, C₇₋₁₂ arylalkyl radicals, C₆₋₁₀ phenoxyradicals, amido radicals which may be substituted by up to two C₁₋₄alkyl radicals and C₁₋₄ alkoxy radicals. In some embodiments, X isselected from a chlorine atom, a methyl radical, an ethyl radical and abenzyl radical.

The Co-Catalyst

The term co-catalyst used herein refers to aluminoxane. Suitablealuminoxane may be of the formula: (R⁴)₂AlO(R⁴AlO)_(m)Al(R₄)₂ whereineach R⁴ is independently selected from C₁₋₂₀ hydrocarbyl radicals and mis from 0 to 50, or, for example, R⁴ is a C₁₋₄ alkyl radical and m isfrom 5 to 30. Methylaluminoxane (or “MAO”) in which each R is methyl isan aluminoxane.

Aluminoxanes are well known as co-catalysts, particularly formetallocene-type catalysts. Aluminoxanes are readily available articlesof commerce.

The use of an aluminoxane co-catalyst generally requires a molar ratioof aluminum to the transition metal in the catalyst from 20:1 to 1000:1.Example ratios are from 50:1 to 250:1.

Commercially available MAO typically contains free aluminum alkyl (e.g.,trimethylaluminum or “TMA”) which may reduce catalyst activity and/orbroaden the molecular weight distribution of the polymer. If a narrowmolecular weight distribution polymer is required, it is preferred totreat commercially available MAO with an additive which is capable ofreacting with the TMA. Alcohols are useful (with hindered phenols beingparticularly useful) for this purpose. In some embodiments, the hinderedphenol is 2,6-di-tert-butyl-4-ethylphenol. If present, the hinderedphenol may be used in amount up to about 0.6 moles per mole of Al. Insome embodiments, the molar ratio of hindered phenol to Al may rangefrom 0.1:1 to 0.5:1, in some embodiments, from 0.15:1 to 0.4:1, in someembodiments, from 0.3:1 to 0.4:1.

“Ionic Activators”

Used herein “ionic activators” refers to activators capable ofabstracting one or more of the activatable ligands in a manner whichionizes the catalyst into a cation, then provides a bulky, labile,non-coordinating anion which stabilizes the catalyst in a cationic form.The bulky, non-coordinating anion permits olefin polymerization toproceed at the cationic catalyst center. Some example ionic activatorsare boron-containing ionic activators described in (i) to (iii) below:

(i) compounds of the formula [R⁵]⁺[B(R⁷)₄]⁻ wherein B is a boron atom,R⁵ is an aromatic hydrocarbyl (e.g., triphenylcarbenium cation) and eachR⁷ is independently selected from phenyl radicals which areunsubstituted or substituted with from 3 to 5 substituents selected froma fluorine atom, a C₁₋₄ alkyl or alkoxy radical which is unsubstitutedor substituted by a fluorine atom; and a silyl radical of the formula—Si—(R⁹)₃; wherein each R⁹ is independently selected from a hydrogenatom and a C₁₋₄ alkyl radical; and

(ii) compounds of the formula [(R⁸)_(t) ZH]⁺[B(R⁷)₄]⁻ wherein B is aboron atom, H is a hydrogen atom, Z is a nitrogen atom or phosphorusatom, t is 2 or 3 and R⁸ is selected from C₁₋₈ alkyl radicals, a phenylradical which is unsubstituted or substituted by up to three C₁₋₄ alkylradicals, or one R⁸ taken together with the nitrogen atom may form ananilinium radical and R⁷ is as defined above; and

(iii) compounds of the formula B(R⁷)₃ wherein R⁷ is as defined above.

In the above compounds, in some embodiments, R⁷ is a pentafluorophenylradical, and R⁵ is a triphenylcarbenium cation, Z is a nitrogen atom andR⁸ is a C₁₋₄ alkyl radical or R⁸ taken together with the nitrogen atomforms an anilinium radical which is substituted by two C₁₋₄ alkylradicals.

The “ionic activator” may abstract one or more activatable ligands so asto ionize the catalyst center into a cation but not to covalently bondwith the catalyst and to provide sufficient distance between thecatalyst and the ionizing activator to permit a polymerizable olefin toenter the resulting active site.

Examples of ionic activators include: triethylammoniumtetra(phenyl)borate; tripropylammonium tetra(phenyl)borate;tri(n-butyl)ammonium tetraphenylborate; trimethylammoniumtetrakis(p-tolyl)borate; trimethylammonium tetrakis(o-tolyl)borate;tributylammonium tetrakis(pentafluorophenyl)borate; tripropylammoniumtetrakis(o,p-dimethylphenyl)borate; tributylammoniumtetrakis(m,m-dimethylphenyl)borate; tributylammoniumtetrakis(p-trifluoromethylphenyl)borate; tributylammoniumtetrakis(pentafluorophenyl)borate; tri(n-butyl)ammoniumtetrakis(o-tolyl)borate; N,N-dimethylanilinium tetraphenylborate;N,N-diethylanilinium tetraphenylborate; N,N-diethylaniliniumtri(phenyl)(n-butyl)borate, N,N-2,4,6-tetramethylaniliniumtetraphenylborate; di-(isopropyl)ammoniumtetrakis(pentafluorophenyl)borate; dicyclohexylammoniumtetraphenylborate, triphenylphosphonium tetraphenylborate;tri(methylphenyl)phosphonium tetraphenylborate;tri(dimethylphenyl)phosphonium tetraphenylborate; tropiliumtetrakis(pentafluorophenyl)borate; triphenylcarbeniumtetrakis(pentafluorophenyl)borate; benzenediazoniumtetrakis(pentafluorophenyl)borate; tropiliumphenyl-tris(pentafluorophenyl)borate; triphenylcarbeniumphenyl-tris(pentafluorophenyl)borate; benzenediazoniumphenyl-tris(pentafluorophenyl)borate; tropiliumtetrakis(2,3,5,6-tetrafluorophenyl)borate; triphenylcarbeniumtetrakis(2,3,5,6-tetrafluorophenyl)borate; benzenediazoniumtetrakis(3,4,5-trifluorophenyl)borate; tropiliumtetrakis(3,4,5-trifluorophenyl)borate; benzenediazoniumtetrakis(3,4,5-trifluorophenyl)borate; tropiliumtetrakis(1,2,2-trifluoroethenyl)borate; triphenylcarbeniumtetrakis(1,2,2-trifluoroethenyl)borate; benzenediazoniumtetrakis(1,2,2-trifluoroethenyl)borate; tropiliumtetrakis(2,3,4,5-tetrafluorophenyl)borate; triphenylcarbeniumtetrakis(2,3,4,5-tetrafluorophenyl)borate; and benzenediazoniumtetrakis(2,3,4,5-tetrafluorophenyl)borate.

Readily commercially available ionic activators include:N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate;triphenylcarbenium tetrakis(pentafluorophenyl)borate (sometimes referredto as trityl borate); and tris(pentafluorophenyl)borane.

In some embodiments, starting ratio of catalyst componentsaluminoxane:catalyst:ionic activator is 100:1:greater than1.1 and isreduced to 50-100:1:0.3-1.05. When such a reduction in the components ismade, the amount of polymer having a molecular weight of 10^(5.3) orgreater is reduced while maintaining the same temperature and mixingconditions in the reactor.

In some further embodiments, the one or more of the components in thecatalyst system could be changed to a different homologue. Typically, insuch embodiments, the homologue would provide a higher degree of sterichindrance at the active metal site.

The polymers produced with the catalyst systems disclosed herein have ahigher CDBI and a lower amount of molecular weight above 10^(5.3). TheCDBI₅₀ composition distribution breadth index (CDBI). The CDBI₅₀ isdefined as the weight percent of the polymer molecules having acomonomer content within 50 percent of the median total molar comonomercontent. The CDBI₅₀ is determined using techniques well known in theart, particularly temperature rising elution fractionation (TREF) asdescribed in Wild et al. Journal of Polymer Science, Pol. Phys. Ed. Vol20, p 441 (1982) or in U.S. Pat. No. 4,798,081. The molecular weightdistribution of a polymer may be determined using GPC (Gel PermeationChromatography. In some embodiments in the polymers disclosed herein,the CBDI₅₀ will be increased by at least about 3%, (e.g., from about 82%to 85% or from 78% to 82%). In some instances, the CBD150 may beincreased by up to 5%.

If Fourier transform IR is also conducted on the sample undergoing GPC,the comonomer incorporation can also be shown graphically.

The present disclosure is applicable to polymers having a density up toabout 0.940 g/cc. At higher densities, the so called higher density peak(really a higher molecular weight peak) is less apparent and, insolution phase polymerization, is usually below 10 wt. %. In someembodiments, the polymers may have a density from 0.905 to 0.935 g/cc.In further embodiments, the polymer may have a density 0.915 to 0.930g/cc. In some embodiments, the polymers also have a melt index (I₂) offrom 1 to 10 g/10 min, in some embodiments, from 2.5 to 7.5 g/10 min. amelt flow ratio (I21/I2) of from 10 to 25 g/10 min, in some embodimentsfrom 15 to 20 g/10 min, a molecular weight distribution (M_(w)/M_(n)) offrom 1.5 to 2.5, in some embodiments, from 1.7 to 2.3.

The amount of copolymer eluting at a temperature of 90° C. or higher,for example, the amount eluting from 90° C. to 105° C., may be reducedby from 5 to 40%, in some embodiments, from 10 to 35%. Such a componentmay have a weight average molecular weight (Mw) from about 225,000 toabout 275,000 (about 10^(5.3) to about 10^(5.5)).

Additionally, the CDBI₅₀ of the polymer may be increased by up to about5%, in some embodiments, up to 4.5%.

Such polymers are useful, for example, in a wide range of applicationsincluding, without limitation, film applications, both blown and cast ofmono or multi-layer films, for various types of packaging; injection,rotational, and blow molding as used for example for small bottles orlarger drums or containers; extrusion of fibers or profiled components;and compression molding for example in small parts.

The present invention will now be illustrated by the following examples.

In the examples, the following catalyst components were used.

The catalyst was cyclopentadienyl tri-t-butyl-phosphinimine titaniumdichloride.

The co-catalyst was methylaluminoxane. It was used in conjunction with ahindered phenol (2,6-di-tert-butyl-4-ethylphenol).

The activator was either triphenylcarbeniumtetrakis(pentafluorophenyl)borate or tris(pentafluorophenyl)borane.

The pilot scale reactor was operated using the following conditions:total flow to the reactor was 450 kg/hr; polymer production rate was 50kg/hr; ethylene concentration 9.3 wt%; weight ratio of 1-octene toethylene 0.6; hydrogen concentration in the reactor 0.5 ppm; primaryfeed temperature 20° C.; Diluent temperature 30.2° C.; reactor meantemperature 163-165° C.; and ethylene conversion at the reactor outlet90%.

The products were tested for a number of properties. Density wasdetermined according to ASTM D-1928; MI (I2) and MFR (I21/I2) weredetermined according to ASTM D1238; molecular weights were determinedusing GPC (Waters 150c with 1,2,4-trichlorobenzene as the mobile phaseat 140° C.) CBDI₅₀ was determined using TREF. One such technique isdescribed in Wild, et al., J. Poly. Sci., Poly. Phys. Ed., vol. 20, p.441 (1982) and U.S. Pat. No. 5,008,204, which are incorporated herein byreference.

Stress exponent is determined by measuring the throughput of a meltindexer at two stresses (2160 g and 6480 g loading) using the proceduresof the ASTM melt index test method, and the following formula:

Stress exponent=1/0.477×log (wt. of polymer extruded with 6480 gwt.)/(wt. of polymer extruded with 2160 g wt.)

Stress exponent values of less than about 1.40 indicate narrow molecularweight distribution while values above about 1.70 indicate broadmolecular weight distribution.

Table 1 shows alternate catalyst system composition.

TABLE 1 Hindered Trityl phenol/ borate/ Borane/ Product Al/catalyst Alcatalyst catalyst Agitator RPM Product 1A 100 0.30 1.2 1170 ComparativeProduct 1B 100 0.30 1.2 400 Comparative Product 2A 50 0.15 0.60 1170Product 2B 50 0.15 0.60 400 Product 3A 100 0.30 0.30 1170 Product 3B 1000.30 0.30 400 Product 4A 100 0.30 1.3 1170 Comparative Product 4B 1000.30 1.3 407 Comparative Product 5A 100 0.30 0.15 1.05 1170 Product 5B100 0.30 0.15 1.05 400 Product 6A 100 0.30 1.20 1170 Product 6B 100 0.301.20 400

TABLE 2 The tests on the products produced in runs 1A, 1B, 2A, 2B, 3Aand 3B. Product Product Product Product Product Product ProductDesignation 1A Comp. 1B Comp. 2A 2B 3A 3B CSTR agitator speed rpm 1170.0400.0 1170.0 400.0 1170.0 400.0 Catalyst Conditions Catalystconcentration in ppm Ti 0.29 0.25 1.15 0.76 1.26 0.88 CSTR Al/Ti ratiomol/mol 100.0 100.0 50.0 50.0 100.0 100.0 Hindered phenol/Al ratiomol/mol 0.30 0.30 0.15 0.15 0.30 0.30 Trityl borate/Ti ratio mol/mol1.17 1.17 0.60 0.60 0.30 0.30 Borane/Ti ratio mol/mol — — — — — —Polymer Properties Density g/cc 0.9187 0.9186 0.9189 0.9187 0.91820.9185 MI (I2) g/10 min 6.16 2.69 6.08 2.88 4.94 2.84 S. Ex. (I5/I2)1.15 1.23 1.12 1.16 1.13 1.17 MFR (I21/I2) 17.4 19.9 15.8 17.4 16.2 17.9M_(n) 30900 40515 36302 41218 30973 42141 M_(w) 57464 87697 65813 8460865992 81578 M_(z) 87414 242449 108741 171581 109425 161667 M_(w)/M_(n)1.9 2.2 1.8 2.1 2.1 1.9 TREF 90-105° C. fraction wt % 3.2 7.7 2.0 6.82.2 6.3 % Reduction in 90° C. to % 38 12 31 18 105° C. fraction comparedto either Product 1A or 1B CDBI₅₀ wt % 82.8 78.4 86.6 82.1 86.1 82.4 %Increase in CBDI₅₀ % 4.6 4.7 4.0 5.1 compared to either Product 1A or 1BElution temperature ° C. 95.0 95.4 93.5 93.6 94.1 95.1 PolymerProperties for 90-105° C. CTREF Fraction SCB/1000 C number 3.4 3.0 3.53.0 M_(n) 110306 139118 137893 151106 M_(w) 224038 274674 243365 261311M_(z) 390537 482660 398845 413780 M_(w)/M_(n) 2.03 1.97 1.76 1.73

Comparing copolymer products produced at the same agitator speed (e.g.,comparing Products 2A and 3A to Product 1A, and comparing Products 2Band 3B to Product 3B) shows that the catalyst composition impacts theamount of polymer eluted at 90 to 105° C. in the TREF analysis.

TABLE 3 The results for the analysis for products 4A, 4B, 5A, 5B, 6A and6B Product Designation Product Product Product Product Product Product4A Comp. 4B Comp. 5A 5B 6A 6B CSTR agitator speed rpm 1170.0 406.61170.0 400.0 1170.0 400.0 Catalyst Conditions Catalyst concentration inppm Ti 0.46 0.40 0.67 0.72 1.18 1.07 CSTR Al/Ti ratio mol/mol 100.0100.0 100.0 100.0 100.0 100.0 BHEB/Al ratio mol/mol 0.30 0.30 0.30 0.300.30 0.30 Trityl borate/Ti ratio mol/mol 1.30 1.30 0.15 0.15 — —Borane/Ti ratio mol/mol — — 1.05 1.05 1.20 1.20 Polymer PropertiesDensity g/cc 0.9192 0.9184 0.9183 0.9187 0.9181 0.9182 MI (I2) g/10 min8.58 3.18 7.16 3.40 5.18 3.02 S. Ex. (I5/I2) 1.16 1.26 1.15 1.23 1.141.18 MFR (I21/I2) 17.5 21.5 16.7 20.0 16.5 17.9 M_(n) 31322 41140 3963436367 33963 38116 M_(w) 59621 80864 66251 75341 68775 77023 M_(z) 127211211343 127785 178707 131624 164903 M_(w)/M_(n) 1.9 2.0 1.7 2.1 2.0 2.0TREE 90-105° C. fraction wt % 3.4 8.6 2.2 7.9 2.3 6.5 % Reduction in 90°C. to 105° C. % 35 8 32 24 fraction compared to either Product 4A or 4BCDBI₅₀ wt % 82.9 77.6 84.8 80.4 86.1 81.3 % increase in CBDI₅₀ 3.2 3.63.9 4.8 compared to either Product 4A or 4B Elution temperature ° C.94.9 95.7 94.8 95.7 94.3 94.7

Again, by comparing copolymers produced at the same agitator speed, onecan see that the type of ionic activator affects the amount of polymereluting at a temperature from 90 to 105° C. in the TREF analysis.

What is claimed is:
 1. A method to increase the homogeneity of a copolymer by reducing the amount of the component eluting at a temperature of greater than 90° C. in the temperature rising elution fraction analysis wherein the copolymer is produced using a solution polymerization process in the presence of a catalyst system comprising:
 1. transition metal catalyst of the formula: (L)_(n)-M-(X)_(p) wherein M is a transition metal, for example a transition metal selected from Ti, Hf and Zr; L is a monoanionic ligand selected from a cyclopentadienyl ligand, an indenyl ligand and a fluorenyl ligand which ligands are unsubstituted or up to fully substituted with one or more substituents selected from chlorine atoms, fluorine atoms and C₁₋₄ alkyl radicals which are unsubstituted or which may be substituted with chlorine or fluorine atoms, and a phosphinimine ligand; X is a monoanionic ligand from the group C₁₋₄ alkyl radicals and chlorine atom; n may be from 1 to 3, and p may be from 1 to 3, provided that the sum of n+p equals the valence state of M, and further provided that two L ligands may be bridged by a silyl radical or a C₁₋₄ alkyl radical;
 2. a boron activator capable of ionizing the transition metal complex selected from: (i) compounds of the formula [R⁵]⁺ [B(R⁷)₄]⁻ wherein B is a boron atom, R⁵ is a cyclic C₅₋₇ aromatic cation or a triphenylcarbenium cation and each R⁷ is independently selected from phenyl radicals which are unsubstituted or substituted with from 3 to 5 substituents selected from a fluorine atom, a C₁₋₄ alkyl or alkoxy radical which is unsubstituted or substituted by a fluorine atom; and a silyl radical of the formula —Si—(R⁹)₃; wherein each R⁹ is independently selected from a hydrogen atom and a C₁₋₄ alkyl radical; and (ii) compounds of the formula [(R⁸)_(t) Z]⁺[B(R⁷)₄]⁻ wherein B is a boron atom, H is a hydrogen atom, Z is a nitrogen atom or phosphorus atom, t is 2 or 3 and R⁸ is selected from C₁₋₈ alkyl radicals, a phenyl radical which is unsubstituted or substituted by up to three C₁₋₄ alkyl radicals, or one R⁸ taken together with the nitrogen atom may form an anilinium radical and R⁷ is as defined above; and (iii) compounds of the formula B(R⁷)₃ wherein R⁷ is as defined above;
 3. an aluminoxane of the formula (R⁴)₂AlO(R⁴AlO)_(m)Al(R⁴)₂ wherein each R⁴ is independently selected from C₁₋₄ alkyl radicals radicals, m is from 3 to 50: and adjusting one or more of: a) the ratio of components 2 and 3; or b) changing component
 2. 2. The method according to claim 1, wherein in the catalyst n is
 2. 3. The method according to claim 2, where in one L is a phosphinimine ligand of the formula:

wherein each R³ is independently selected from a hydrogen atom; a halogen atom; C₁₋₁₀ hydrocarbyl radicals which is unsubstituted by or further substituted by a halogen atom; a C₁₋₈ alkoxy radical; a C₆₋₁₀ aryl or aryloxy radical; and an amido radical which is unsubstituted or substituted by up to two C₁₋₁₀ hydrocarbyl radicals.
 4. The process according to claim 3, wherein the reaction temperature is from 80° C. to 180° C. and the pressure is from 6,000 kPa to 22,000 kPa.
 5. The process according to claim 4, wherein the starting ratio of catalyst components aluminoxane:catalyst:ionic activator is 100:1:greater than 1.1 and is reduced to 50-100:1:0.3-1.05.
 6. The process according to claim 5, where in the ionic activator is selected from triphenylcarbenium tetrakis(pentafluorophenyl)borate and tris(pentafluorophenyl)borane.
 7. The method according to claim 6, wherein the aluminoxane is methyl aluminoxane which may be used in conjunction with a hindered phenol to provide a molar ratio of hindered phenol:Al up to 0.6:1.
 8. The method according to claim 7, wherein the catalyst is cyclopentadienyl tri-tert-butylphosphinimine titanium dichloride.
 9. The method according to claims 8, wherein the catalyst is alkylated within ten minutes prior to use. 